In regard to fisheries, depressed is the condition of a fishery for which the best available scientific information, and other relevant information that the Commission or Department possesses or receives, indicates a declining population trend has occurred over a period of time appropriate to that fishery. With regards to fisheries for which management is based on maximum sustainable yield, or in which a natural mortality rate is available, depressed means the condition of a fishery that exhibits declining levels of fish abundance below those consistent with maximum sustainable yield.